The patent FR 2 668 234, in the name of the Applicant, discloses a torque converter comprising an impeller wheel integral with a cover intended to be coupled to an engine crankshaft, with the impeller wheel being able to hydrokinetically drive the turbine wheel through the reactor.
The torque converter also comprises clutch means comprising a piston axially movable between an engaged position in which it is friction-coupled to the cover and a disengaged position in which it is uncoupled from the cover. The piston is connected to the hub through damping means. Said damping means comprise elastic springs acting circumferentially. The hub is intended to be coupled to a transmission input shaft. Besides, the turbine wheel is rotationally coupled to the hub.
Pressure chambers are provided on either side of the piston so that the latter is moved according to the pressure difference between said chambers.
In the disengaged position of the piston, the torque generated by the crankshaft is transmitted to the cover and to the impeller wheel, which hydrokinetically drives the turbine wheel through the reactor. The torque is then transmitted to the hub and to the transmission input shaft. The above-mentioned elastic damping means are not active in such an operating mode.
On the contrary, in the engaged position of the piston, the torque generated by the crankshaft is transmitted to the cover, and then to the piston friction-coupled to said cover. The torque is then transmitted to the hub and to the transmission input shaft, through the damping means.
Depending on the specifications, it may be necessary to have a normally closed torque converter, i.e. which, when in the engaged position, is in a so-called rest position in which the piston is not controlled. Reducing the duration of the clutch engaging phase, i.e. the time required to change from a disengaged position to an engaged position, may also be necessary. Increasing the torque which can be transmitted through the clutch may also be required.
Besides, the damping means used are relatively expensive, have a complex structure, i.e. a significant number of parts, and are cumbersome.